Electric generators are essential appliances that supply electrical power during a power outage and prevent disruption of daily activities or business operations. In this post, we will take a look at how a generator functions, the main components and parts of a generator, and how a generator functions as a secondary source of electrical power in residential and industrial locations.

How does a generator function?

An electric generator is a device that converts mechanical energy acquired from an external source into an output of electrical power.

It is important to understand that an electric generator does not actually 'create' electrical energy. It instead uses the mechanical energy supplied to it to force the movement of electric charges present in its windings through an external electric circuit. This flow of electric charges makes up the output electric current supplied by the generator. We can understand the mechanism of a generator by considering the generator to be analogous to a water pump. It leads to water flow but does not actually 'create' the water flowing through it.

Main components of a generator

A description of the nine main components of a generator is given below.


The engine is the origin of the input mechanical energy to the generator. The size of the engine is directly related to the maximum power output the generator can supply. There are several aspects that you need to keep in mind while assessing the engine of your generator:

(a) Type of Fuel Used – Generator engines can operate on different fuels such as diesel, gasoline, propane, or natural gas. Generators with smaller engines usually operate on gasoline, while larger engines typically operate on diesel, liquid propane, propane gas, or natural gas. Some engines can also operate on a dual feed of both diesel and gas in a bi-fuel operation mode.

(b) Overhead Valve (OHV) Engines versus non-OHV Engines – OHV engines are different from other engines because the intake and exhaust valves of the engine are located on the top of the engine's cylinder instead of being mounted on the engine block. OHV engines have some advantages over other engines such as:

  • Compact design
  • Simpler operation mechanism
  • Durability
  • User-friendly in operations
  • Low noise during operations
  • Low emission levels

Keep in mind that OHV-engines are also more expensive than other engines.

(c) Cast Iron Sleeve (CIS) – The CIS is a lining in the engine's cylinder. It reduces the wear and tear of the engine and ensures durability. Most OHV-engines are usually equipped with CIS, but it is essential to check for this feature in the engine of a generator. The CIS is not an expensive feature, but it plays a crucial role in the engine's durability, especially if you use your generator often or for long periods.



The alternator is also called the 'genhead'. It is the part of the generator that produces the electrical output from the mechanical input the engine supplies. It consists of an assembly of stationary and moving parts encased in a housing. The parts work together to create relative movement between the magnetic and electric fields, generating electricity.

(a) Stator – This is the stationary component of the alternator. It contains a set of electrical conductors wound in coils over an iron core.

(b) Rotor / Armature – This is the moving component of the alternator that produces a rotating magnetic field.


Fuel System

The fuel tank usually has enough capacity to keep the generator running for an average of 6 to 8 hours. In smaller generator units, the fuel tank can be a part of the generator's skid base or is situated on top of the generator frame. It may be necessary to erect and install an external fuel tank in bigger generators. Some typical features of the fuel system include the following:

(a) Pipe connection from the fuel tank to the engine – The supply line leads fuel from the tank to the engine, and the return line leads fuel from the engine back to the tank.

(b) Ventilation pipe for the fuel tank – The fuel tank has a ventilation pipe that prevents the build-up of pressure or vacuum during refilling and drainage of the tank.

(c) Fuel pump – This transports fuel from the primary storage tank. The fuel pump is usually electrically operated.

(d) Fuel Water Separator / Fuel Filter – This separates water and other contaminants from the fuel to protect other generator parts from corrosion and contamination.

(e) Fuel Injector – This breaks down the fuel and sprays the amount of fuel required into the engine's combustion chamber.


Voltage Regulator

As the name says, this part of the generator regulates the output voltage. The voltage regulator converts the generator's AC voltage output into direct current (DC). The voltage regulator then sends the DC to a set of secondary windings in the stator, known as exciter windings, which converts the DC to AC.


Cooling & Exhaust System

(a) Cooling System

Continuous usage of the generator causes its various parts to heat up. It is necessary to have a cooling system to discharge the heat produced.

Raw/freshwater can be used as a coolant for generators. For all other common uses, a standard radiator and fan are mounted on the generator, which works as the primary cooling system.

It is very important to check the coolant levels of the generator daily. The generator should be operated in an open and ventilated area with an adequate fresh air supply. It is advised that a minimum space of 3 feet should be allowed on all sides of the generator to ensure the free flow of air.

(b) Exhaust System

Exhaust fumes emitted by a generator are highly toxic chemicals that need to be properly disposed of. Therefore, it is essential to install an adequate exhaust system to dispose of the exhaust gases. 


Lubricating System

Since the generator comprises of several moving parts in its engine, it requires lubrication to ensure exceptionally smooth operations for an extended period. The generator's engine is lubricated by engine oil stored in a pump. You should check the level of oil every 8 hours of use. You should also check for any oil leakages and change the lubricating oil every 500 hours of use.


Battery Charger

The battery charger usually keeps the generator battery charged by supplying a specific 'float' voltage. If the float voltage is too low, the battery will remain undercharged. If the float voltage is too high, it will shorten the life span of the battery.


Control Panel

The control panel is the user interface of the generator and has provisions for electrical outlets and controls. Different manufacturers have numerous features to offer in the control panels of their units.


Main Assembly/Frame

All generators have customized housings that provide a structural base of support. The frame also allows for the generator to be earthed for safety reasons.


Now you have a description of each part of generator and how they work together to provide electricity. If you enjoyed this article, feel free to sign up on our website to get the most professional advice from our experts.